Hydraulically actuated motor vehicle clutch of the pull to release type

ABSTRACT

A friction clutch of the pull to release type, includes a clutch casing (10) within which there is arranged a declutching control device (20), which comprises a clutch release bearing and a hydraulic actuating device (26, 34) that comprises at least one actuating piston (34), which is arranged to urge the clutch release bearing (20) axially in a first direction (F1) so as to disengage the clutch when the hydraulic actuating device is supplied with fluid under pressure, together with a lever (44) having a body (46), a first end portion (50) and a second end portion (60). The body (46) of the lever (44 extends through an oblong aperture formed in the wall of the casing (10), while the second end portion of the lever (44) projects outside the casing (10) so as to enable the clutch release bearing (20) to be urged, through the piston (26, 34), axially in a second direction (F2) opposite to the first direction (F1).

BACKGROUND OF THE INVENTION

a) Field of the Invention

The present invention relates to a friction clutch, especially for amotor vehicle.

The invention is concerned more particularly with a clutch of the pullto release type, one embodiment of which is described and shown in thedocuments FR-A-2 304 826, FR-A-2 653 195 (U.S. Pat. No. 5,113,989),DE-A-2 815 971.

b) Description of Related Art

A clutch of this type comprises a friction disc which is disengageablycoupled in rotation to a rotatable drive shaft (the crankshaft of theengine in the case of a motor vehicle), a control member which isarranged to control disengagement of the friction clutch from the driveshaft when an axial tractive force is exerted on it, and a clutchrelease bearing which is arranged to work axially in traction on thecontrol member of the clutch.

Such a clutch, as shown in the document FR-A-2 304 826, may be of themechanically controlled type, that is to say of the type which has afork for control of the declutching operation, which is made in the formof a lever pivoted on the clutch casing, with its inner end workingaxially on a sliding sleeve, one end of which is coupled axially, forexample, to the outer ring of the ball bearing which is part of theclutch release bearing.

As described in that document, the use of the mechanical declutchingcontrol fork, in a direction opposite to that which provides thedeclutching function, enables an element coupled to the inner ring ofthe ball bearing of the clutch release bearing to be coupled, in fixedrelationship in an axial tractive mode, with a component which works ona diaphragm or on declutching levers, this coupling being obtained bymeans of resilient mating which may also be called clipping.

Various clutch designs are also known which include a hydraulicactuating device that includes at least one actuating piston, one end ofwhich works on the clutch release bearing so as to urge the said releasebearing axially in a first direction, in order to disengage the clutchwhen the hydraulic actuating device is supplied with fluid from apressurized fluid source, such as for example a clutch cylinder.

One example of such a hydraulically actuated clutch is described andshown in the document U.S. Pat. No. 3,955,660, in which the actuatingpiston is made in the form of a cylindrical sleeve mounted for slidingmovement on a cylindrical guide surface fixed to the clutch casing.

Such a hydraulically actuated clutch, which no longer includes amechanical actuating fork for the clutch release bearing, does notenable initial fastening, by means of resilient mating, to be obtainedbetween the output member of the clutch release bearing and the memberwhich acts on the pressure plate.

Such a type of clutch also has other disadvantages, among which arethose related to the supply of pressurized fluid to the actuatingchamber of the hydraulic piston, which makes it necessary to provide atleast one pressurized fluid supply duct which extends inside the clutchcasing, and which can be connected hydraulically to the actuatingchamber and to the pressurized fluid source, and in connection withwhich, in the interest of its good mechanical strength, it is in generalnecessary to provide means for preventing rotation of the actuatingpiston.

Such means are described in the document DE-A-2 815 971. In this latter,the hydraulic actuating device further includes a mechanical leverhaving a body, a first end portion coupled in axial translation to thepiston and pivoted on the latter about a pivot axis at right angles tothe axis of axial sliding movement of the piston, and a second endportion, with the said lever passing through a cylindrical hole in thewall of the casing.

In practice it is the second end portion of the lever that extendsthrough the wall of the casing, being flush with the latter.

With this type of embodiment, it is not possible to carry out initialfastening, by resilient mating, between the output member of the clutchrelease bearing and the member which acts on the pressure plate.

SUMMARY OF THE INVENTION

An object of the present invention is to propose a new design for ahydraulically actuated clutch of the pull to release type, whichprovides a remedy for the disadvantages which have just been described.

In accordance with the invention, a friction clutch of the pull torelease type having a lever, of the type described above, ischaracterized in that the body of the mechanical lever extends throughan oblong aperture formed in the wall of the casing, in that the secondend portion of the mechanical lever projects outside the casing so as toenable the clutch release bearing to be urged axially, through thepiston, in a second direction opposite to the first direction so thatthe said mechanical lever is an actuating lever.

Preferably, the second end portion of the actuating lever is profiledfor cooperation with a tool.

For example, this second end portion may consist of a head into which ahollow tool can penetrate in a complementary manner.

By virtue of these arrangements it is possible to displace the pistonaxially in its second direction in order to snap-fit the clutch releasebearing on its associated actuating member.

In normal operation, the said lever does not hinder the displacement ofthe release bearing, because the aperture in tile casing is oblong inform, the dimension of the said aperture being a function of thedisplacement of the piston.

In accordance with further features of the invention:

the pivot axis of the lever is offset radially with respect to the axisof the piston;

the first end portion of the lever is in the form of a fork;

the body of the lever extends through a window formed in a wall of thecasing, and the second end portion of the lever projects outside thecasing;

the hydraulic actuating device includes a supply circuit for fluid underpressure, comprising at least one feed duct which connects the actuatingchamber for the piston to a source of fluid under pressure arrangedoutside tile casing, at least a part of being formed in the body of thelever;

the body of the lever includes a longitudinal duct, a first end of whichis connected to the actuating chamber for the piston through means forpivoting the said first end portion of the lever on the piston;

the second end of the duct is open on the outside of the clutch casing;

the supply circuit includes a purge duct, at least part of which isformed in the body of the lever.

The purge duct is associated with a threaded purge plug. In this waypurging can be carried out on the outside of the casing and in anaccessible position. The threaded purge plug may of course be arrangedin another position on the lever or outside the latter.

It will be noted that the radial offset of the pivot axis of the leverwith respect to the axis of the piston facilitates the supply of fluidto the actuating chamber through the lever, and also facilitates purgingof the supply circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention will appear on areading of the detailed description which follows, and for anunderstanding of which reference is made to the attached drawings, inwhich:

FIG. 1 is a diagrammatic partial view in axial cross section, showingpart of a clutch casing and the actuating device for the clutch releasebearing made in accordance with the invention;

FIG. 2 is a view in cross section taken on the line 2--2 in FIG. 1;

FIG. 3 is a detail view on a larger scale, showing part of FIG. 2; and

FIG. 4 is a detail view on all enlarged scale showing a modifiedembodiment of the device shown in FIGS. 1 to 3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The drawings show a clutch casing 10 which is part of a motor vehicleclutch of the "pull to release" type, being hydraulically actuated.

Not all of the clutch is shown in the drawings and it will not bedescribed in detail, and reference can be made in particular to tiledocuments previously cited herein for familiarization with variousembodiments thereof.

It will be recalled that the motor vehicle clutch commonly comprises afriction disc having friction liners at its outer periphery, a reactionplate, a pressure plate which is movable axially with respect to thereaction plate, a cover plate fixed to the reaction plate, and axiallyacting resilient means which engage on the cover plate and on thepressure plate, in order to clamp the friction liners between thepressure and reaction plates, which are fixed with respect to thecrankshaft of the engine for rotation with it, while the friction discis mounted on the input shaft of the gearbox for rotation with thelatter.

The axially acting resilient means are part of the declutching devicefor the clutch, and comprise either a diaphragm as in the documentFR-A-2 304 826, or coil springs associated with declutching levers, asin the document U.S. Pat. No. 3,995,660.

It will be recalled that in a diaphragm clutch of the pull to releasetype, the said diaphragm engages on the cover plate through the outerperipheral portion of its Belleville ring, and, through the innerperiphery of its said Belleville ring, on an engagement land, which iscommonly of divided form, of the pressure plate.

An actuating member is associated with the declutching levers or withthe diaphragm, and for disengagement, or declutching, of the clutch itis necessary to work in traction on the actuating member by means of aclutch release bearing which is coupled to the actuating member.

Actuation of the release bearing is obtained by means of a hydraulicactuating device which comprises, in a manner described below, anaxially movable piston 26, 34, an axially fixed guide member 16, ahydraulic actuating chamber 38 for the piston which is delimited by theguide member 16 and by the piston, and a supply circuit for fluid underpressure, which comprises at least one supply duct that connects theactuating chamber for the piston to a pressure source, for example aclutch cylinder on which the clutch pedal acts.

The pressure source is arranged, in a manner known per se, outside thecasing 10. The casing 10 is generally in the form of a hood, and has aradial end wall 12, on tile internal surface 14 of which there issecured, axially and in rotations, a post 16, also referred to as ahorn, which has a cylindrical outer engagement surface 18 defining anaxis X--X.

The casing 10 encloses, in particular, a clutch release bearing 20 whichconsists essentially of a ball bearing 22, the outer ring 24 of which issecured, in this example by seaming, to an actuating sleeve 26 forrotation with the latter, with the rotatable inner ring 28 of the saidbearing being extended by a sleeve portion 30 which has, in particular,an external radial groove 32 which is arranged to receive tractivecoupling means which provide a resilient axial mating connection (notshown) with the actuating member of the clutch (not shown) and thereforewith the diaphragm or declutching levers. For more details, reference ismade to the documents FR-A-2 304 826 and FR-A-2 653 195 (U.S. Pat. No.5,113,989), the tractive coupling means normally comprising a radiallyresiliently deformable coupling such as a coupling ring, fitted in tilegroove 32 and making engagement with a surface of the actuating member.

Actuation of the clutch release bearing 20 is obtained by means of ahydraulic actuating device which comprises an actuating piston,consisting of the hollow cylindrical body 34 of the sleeve 26, the innercylindrical surface 36 of which cooperates at the rear end of the sleevewith the cylindrical surface 18, so as to define a hydraulic actuatingchamber 38. The post 16 thus constitutes a guide member for the piston26, 34, and is in a piston and cylinder relationship with the saidpiston 26, 34.

It win be noted that the piston 26, 34 is able to move the clutchrelease bearing 20 axially, the said piston having, as mentionedearlier, an end portion which acts on the clutch release bearing 20.

This release bearing 20 is coupled in axial translation to the piston,by which it is carried.

In the drawings, the coupling is obtained by a seamed connection, but ina modification, as described in the document DE-A-2 815 971, thiscoupling may be obtained by force-fitting the outer ring 24 of therelease bearing 20 on to the associated end of the piston 26, 34, withthe said end being accordingly formed with a shoulder.

As described in the document FR-A-2 304 826, it is of course possible toreverse the structures, with the inner ring of the bearing 20 then beingcoupled axially to the piston 26, 34, while the outer ring of thebearing 20 is rotatable, being coupled in axial mating relationship tothe actuating member.

More precisely, the hydraulic actuating chamber 38 is delimited axiallyby two grooved sealing rings 40 and 42, which are carried respectivelyby the piston 26, 34 and by the horn 16. To this end, the piston 26, 34has at its rear end a collar portion which is directed towards the axisof the assembly, while the post 16 has at its forward end a thrust ringwhich is located axially by a circlip.

The sealing rings 40, 42, which are in the form of lipped sealing rings,are engaged respectively on the collar and on the thrust ring, with apre-loading spring being interposed for urging the release bearing 20and the piston 26, 34 towards the wall 12, so as to exert a pre-loadingforce on the clutch and so as to ensure good operation of the ballbearing of the release bearing 20 in a manner known per se.

A protective bellows is arranged between the rear ends of the piston 26,34 and post 16.

When the actuating chamber 38 is supplied with fluid under pressure, bymeans which win be described later herein, it produces an axialdisplacement of the piston 26, 34 along the axis X--X, in the directionF1 from left to right in FIG. 1, in such a way as to cause disengagementof the clutch to be effected by axial displacement of the clutch releasebearing 20.

In accordance with the invention, a lever 44 is provided, whichdisplaces the piston 26, 34 and the clutch release bearing 20 axially inthe opposite direction as indicated by the arrow F2, that is to say fromright to left in FIG. 1, for the purpose of assembling the clutchrelease bearing to its actuating member as in the document FR-A-2 304826. This lever extends partly outside the casing 10.

More precisely, in accordance with the invention, the lever 44 comprisesa lever body 46 which extends through the conical portion 13 of the wallof the clutch casing 10, via an oblong hole 48, which in this example isin the form of a window with a rectangular cross section, the length ofwhich extends axially parallel to the axis X--X.

The lower end portion 50 of the lever 44, which is arranged inside theclutch casing 10, is in this example made in the form of a fork havingtwo arms 50A and 50B, which are connected to the body 34 of the pistonconstituted by the sleeve 26.

For this purpose, each of the branches 50A, 50B of the fork-shaped endportion 50 has, passing through it, a pivot screw 52A, 52B, the threadedend portion of which is screwed into the upper part of the sleeve 34,with its body portion 56A, 56B passing through a corresponding aperture58A, 58B formed in the end of the arm, so as to define an axis Y--Y forpivoting of the lever 44 n the sleeve 34, which is offset radiallyoutwardly with respect to the axis X--X along which the piston 34slides.

The second end portion 60 of the lever 44 projects outside the casing 10in such a way that it is possible to work mechanically on the lever 44,for example by means of a tool 62 indicated diagrammatically in FIG. 1,with a view to increasing the lever arm. This end portion 60 is profiledaccordingly, and consists for example of a head into which the hollowtool 62 is inserted in a complementary manner.

It win easily be understood that application of an external mechanicalforce on the end portion 60 of the lever 44, by causing it to pivot inthe clockwise direction with reference to FIG. 1, about a pivot pointresulting from the contact of its body 46 with the corresponding edge ofthe window 48, produces an axial displacement of the piston 26, 34 inthe direction indicated by the arrow F2.

This facility for mechanical actuation of the piston 26, 34 is made useof during assembly of the clutch, in order to secure the inner ring 28,30 axially with the actuating member, this being done in accordance withan axial mating technique such as that described and shown in thedocument FR-A-2 304 826.

In accordance with another aspect of the invention, the lever 44includes part of the pressurized fluid supply circuit for the piston 26,34. This is made possible due to the fact that the second end portion 60of the lever projects outside the casing 10, as does the body 46, sothat it is easy to make duct connections.

To this end, the branch 50A includes a feed duct 64A, for supplyingfluid under pressure and having an inner end 66A which is connected tothe actuating chamber 38, with its outer end 68A being connected,through a coupling 70A, to a pressurized fluid pipe 72 which is itselfconnected to a clutch cylinder (not shown).

The hydraulic connection of the end 66A of the feed duct 64A is shown indetail in FIG. 3, from which it can be seen that it is open into aradial groove 74A on the smooth body of the screw 52A that defines thepivot axis, with the groove 74A being itself connected to an axialpassage 76A formed within the screw, which is open into a coaxial duct78A formed in the body 34 of the piston and exhausting into theactuating chamber 38.

Sealing of tile joint is provided by means of two O-rings 80A.

The second branch 50B of the fork-shaped lower end portion 50 of thelever 44 also includes a longitudinal purge duct 64B, the upper end 68Bof which is connected to a threaded purge plug 70B, with its lower endbeing connected to the chamber 38 through an arrangement which isidentical with that of the inner end 66A of the feed duct 64A.

Because of this aspect of the invention there is no longer any flexiblepipe with the clutch casing, and the piston 26, 34 is also preventedfrom rotating by the mechanical actuating lever 44 which, for thispurpose, extends through the window 48 of the casing 10 with a clearanceon the plane of FIG. 1, for the axial displacement of the piston 26 andthe release bearing 20, there also being a reduced clearance in theplane of FIG. 2 for preventing rotation of the piston 26.

The body portion 46 of the lever 44 therefore passes, parallel to tileaxis X--X (in the axial direction) and with an axial clearance, throughthe window 48, and with a reduced clearance in the other direction. Theaxial clearance does not perturb the displacement of the piston 26 innormal operation.

The aperture 48 can of course be axially oblong (parallel to the axisX--X), with rounded ends.

It is of course possible to coat the edges of the window 48 withplastics material, for example one having a low coefficient of friction,so as to reduce noise and friction.

The modified embodiment shown in FIG. 4 win now be described, in whichthose parts that are identical or similar to those in the embodimentshown in FIGS. 1 to 3 are indicated by the same reference numerals.

In this embodiment, the lever 44 has a body 46 which terminates at itsinner end 50 in the form of a single lever, which extends laterally onone side of the sleeve-shaped body 34 of the piston 26.

As before, the pivot axis Y--Y of the lever 44 is offset radially withrespect to the axis X--X of the piston 34.

The body 46 and the single arm 50 include the feed duct 64A and purgeduct 64B, which are both open in facing relationship with radial grooves74A, 74B formed in the body of the single pivot screw 52.

It win be appreciated that the grooved sealing rings 40, 42 areprotected because the piston 26, 34 is prevented by the lever 44 fromrotating.

The pre-loading spring may of course, as call be seen in broken lines inFIG. 1, act between the end portion 60 of the lever and the casinginstead of acting between the grooved sealing rings 40, 42.

Besides good operation of the ball bearing of the release bearing 20,this arrangement prevents vibrations at the lever 44. Protective bellows(FIG. 1) can of course be arranged between the window 48 and the endportion 60 of the lever 44. The threaded purge plug may be fitted eitheron the piston 26, or in another position on the lever 44.

Finally, the pivot axis of the lever 44 may be arranged so that it isnot offset radially with respect to the axis of the piston.Nevertheless, this arrangement is less favourable, because it extendsthe length of the feed duct formed in the lever 44. Besides which, it ismore difficult to purge the supply circuit.

As win have been understood, this is the reason why, in FIGS. 1 to 4,the pivot screws 512, 52A, 52B have been arranged in the upper part ofthe piston 26, 34 and chamber 38.

I claim:
 1. A friction clutch of the pull to release type, comprising aclutch casing (10), within which there is arranged a declutching controldevice (20) which comprises, firstly, a clutch release bearing (20),secondly a hydraulic actuating device (26, 34) comprising at least oneactuating piston, one end of which works on the clutch release bearing(20) to urge said release bearing (20) axially in a first direction(F1), so as to cause declutching to take place when the hydraulicactuating device is supplied with fluid under pressure, and, thirdly, amechanical lever (44) having a body (46), a first end portion (50)coupled in axial translation with the piston (26, 34) and pivoted on thepiston about a pivot axis (Y--Y) at right angles to the axis (X--X) ofaxial sliding movement of the piston (26, 34), and a second end portion(60), with said lever (44) extending through the wall (13) of the casing(10), characterized in that the body (46) of the mechanical lever (44)extends through an oblong aperture (48) formed in the wall of the casing(10), in that the second end portion (60) of the mechanical leverprojects outside the casing so as to enable the clutch release bearing(20) to be urged axially, through the piston (26, 34), in a seconddirection (F2) opposite to the first direction (F1), so that themechanical lever (44) is an actuating lever.
 2. A clutch according toclaim 1, characterized in that the second end portion (60) is profiledfor cooperation with a tool (62).
 3. A clutch according to claim 1,characterized in that the body (46) of the lever (44) extends throughthe oblong aperture (48) of tile casing (10) with a clearance in theaxial direction parallel to the axis (X--X) of axial sliding movement ofthe piston (26, 34), for axial displacement of the piston (26) andclutch release bearing (20), and with a reduced clearance in the otherdirection so as to prevent rotation of the piston (26).
 4. A clutchaccording to claim 1, characterized in that the pivot axis (Y--Y) of thelever (44) is offset radially with respect to the axis (X--X) of thepiston (26, 34).
 5. A clutch according to claim 1, characterized in thatthe first end portion (50) of the lever is in the form of a fork (50A,50B).
 6. A clutch according to claim 1, characterized in that the firstend portion (50) of the lever comprises a single arm which extends onone side of the piston (26).
 7. A clutch according to claim 1,characterized in that the hydraulic actuating device includes a supplycircuit for fluid under pressure, comprising at least one feed ductwhich connects the actuating chamber (38) for the piston (26, 34) to asource of fluid under pressure arranged outside the casing (10), and inthat at least a part (64A) of said duct is formed in the body (46) ofthe lever (44).
 8. A clutch according to claim 7, characterized in thatthe body of the lever includes a longitudinal duct (64A), a first end(66A) of which is connected to the actuating chamber (38) for the piston(26, 34) through means (52A) for pivoting said first end portion (50A)of the lever (44) on the piston (26, 34).
 9. A clutch according to claim8, characterized in that the second end (68A) of the duct (64A) is openon the outside of the clutch casing (10).
 10. A clutch according toclaim 7, characterized in that the supply circuit includes a purge duct(64B), at least part of which is formed in the body (46) of the lever(44).